THE ROLE OF THE ORTHODONTIST IN ORTHOGNATHIC SURGERY

THE ROLE OF THE ORTHODONTIST IN ORTHOGNATHIC SURGERY

I/- INTRODUCTION

The field of maxillofacial surgery is vast, encompassing a wide variety of procedures that operate at the crossroads of orthopedic and functional therapies.
Maxillofacial surgery targets both hard and soft tissues to improve aesthetics and function, and requires close collaboration between the surgeon and the orthodontist.
The latter may intervene before, during, or after surgery and is an essential element in establishing the therapeutic approach.

II/- DIAGNOSTIC STUDY AND DECISION ELEMENTS

II-1/- Diagnostic study

The initiation of surgical or surgical-orthodontic therapy requires a complete clinical examination of the patient, in order to best assess the type and extent of the dysmorphosis as well as the patient’s motivations, which may be aesthetic or functional.
This therapeutic approach is carried out simultaneously by both specialists.
As far as the orthodontist is concerned, it is carried out as follows:

1)- Anamnesis

a)- Psychological evaluation

It is done through a simple interview between the patient, who will easily express his motivations by listening to him more than by questioning him.
The motivations can be:

Functional : This involves either:
- From discomfort when chewing due to occlusal deficit.
- From an occlusal imbalance without orthodontic possibilities.
- Difficulty in fitting due to partial or total tooth loss, due to the shift in bases.
Aesthetic : following a defect in the appearance of the face, due to a deviation of the chin for example.
Psychological : the subject does not like the appearance of his face which presents a deficit and feels bad about himself.

All these elements help the practitioner to determine the patient’s psychological background and the possibilities of carrying out the therapeutic act.

b)- Pathological history

Orthodontic history
Their existence allows, in collaboration with the orthodontist who is following the patient, to clarify the diagnosis made and to establish a joint treatment plan.
General background
Allows to determine the existence of:
- From a pathological defect, contraindicating the intervention.
- From a mental deficit preventing post-operative care and monitoring.
- Determine the stage of bone growth.

2) Clinical examination

a) Deformation analysis

Above all, it allows us to note the external impact of the disfigurement on the face and the occlusion, at rest and during functional movements.

b) Study of functional disorders

The examination of all orofacial functions is of paramount importance, as any abnormality at this level can compromise the final result of surgery and cause relapses.
This means that any surgical-orthodontic treatment must be preceded by rehabilitation of the disturbed functions.

c) Dental and occlusal examination

It allows you to appreciate:

The importance of dysmorphosis.
Orthodontic possibilities.
The problems of available space.
The effects of surgical treatments on occlusion.
The effects of occlusion on other components of the stomatopathic system.

d) Periodontal examination

It is essential because any lesion could alter the long-term prognosis. For some authors, pre-existing periodontal lesions in adults are aggravated by orthodontic movements and traumatic occlusion, which will favor orthopathic surgery to avoid the risks of rhizalysis by reducing dental movements. For KENT and HIND, the only periodontal problems are located at the level of the vertical osteotomy line between two teeth, with a small interdental space.

3) X-ray examination

An essential complement, it allows, thanks to techniques and indices, to establish a precise diagnosis of maxillomandibular dysmorphosis.

a) TLRX

Thanks to cephalometric analyses, they specify and quantify the dysmorphosis.

In profile
- They allow the study of the position of dental, bone and alveolar elements in the sagittal and vertical direction.
From the front
- They are used in cases of asymmetry.

b) Wrist X-ray

It allows bone age to be determined.

c) Tomographies

From the front and side of the condyles, it provides information on cases of asymmetry and lateromandibular joint movement.

d) The orthopantomogram

It allows an overview of the alveolo-dental arches, and notes the presence or absence of inclusions or cystic deformations, as well as a visualization of the condyles, symmetry and mandibular shape.

e) The retroalveolar

It allows precise visualization of the surgical area and the relationships of the section line with the teeth.

f) Xerography and scanning

They provide accurate information regarding soft and hard tissues.

II-2/- Elements of decision

Surgical-orthodontic therapy must take into account several factors, including:

Associated pathologies
These should never be lost sight of, as their management could lengthen or even modify the therapeutic program.
Age
The patient’s age is a key point in surgical-orthodontic care.
The rule is to wait:

For dysmorphic defects, the development of the second permanent molars and the regular onset of menstruation in young girls. (average age: 15-14 years).
For excessive dysmorphisms, the end of growth (18 years in boys, 16 years in girls), after radiographic control of the left wrist and successive comparative TLRX. Despite all this, it is necessary to keep in mind the existence of a late terminal growth spurt, particularly in boys.
However, early intervention is required in the presence of excessive promandibulia, which is functionally and socially embarrassing.

Motivation
The patient’s initial motivation, age, environment, family and cultural heritage, as well as the psychological profile, are all factors to be perceived, analyzed and taken into account in the therapeutic decision.
Prediction of associated gestures
The correction of maxillomandibular dysmorphoses can lead to the performance of additional gestures, such as:

Genoplasty.
Correction of a deviated nasal septum.
Rhinoplasty…etc.

III/- SURGICAL-ORTHODONTIC INTERRELATIONSHIP AND THERAPEUTIC APPROACH

The initiation of orthognathic surgery requires collaboration between the surgeon and the orthodontist, because any single-disciplinary action forces the practitioner to “cheat” to obtain results, which will in any case be unsatisfactory from an aesthetic and functional point of view. This collaboration is based on a mutual knowledge of the 2 specialties with regard to:

The nomenclature.
The diagnostic approach.
Therapeutic means.

Orthodontic-surgical treatment includes five phases, which follow one another chronologically as follows:

Phase 1 : preparatory or planning and information.
Phase 2 : Pre-surgical orthodontics.
Phase 3 : surgical.
Phase 4 : Post-surgical orthodontics.
Phase 5 : containment and additional treatments.

1) Phase 1 “preparatory or planning and information”

During this phase, the patient is examined separately by the two specialists, in order to:

To better explain the specificities of their treatment.
To classify problems according to their degrees of severity.

After the synthesis of the solutions envisaged, the treatment plan is jointly established as well as the practical aspects of the overall care, emphasizing the pre- and post-surgical phases. At least three months before the intervention, the oral cavity will be restored during this phase by:

Establishment of good oral hygiene.
Extractions and endodontic care.
Temporary prosthetic restorations, after removal of questionable prostheses and occlusal equilibration.
Periodontal treatment if necessary, because in certain promandibulias it is necessary to perform vestibular mucosal grafts before decompensation by vestibulo-version of the lower incisors.
Dental and periodontal reassessment.
Avulsion of the included DDS at least 6 months before the intervention, thus avoiding the risk of bone fracture during cleavage, or the difficulties of placing the osteosynthesis plates by bi-cortical cleavage.

In addition to these points, this phase is also essential to do:

An examination of the tongue and its behavior, at rest and in function, because an increased volume could compromise a mandibular osteotomy, aimed at reducing the lingual environment.
Search for a reliable mandibular-cranial position.
Note the relationship of dysmorphosis to this position.

2) Phase 2 “pre-surgical orthodontics”

Its purpose is:

To decompensate the alveolar-dental anomaly, in order to reveal the exact shift of the bases.
To plan the dental movements to be carried out depending on the osteotomies, so that they do not hinder the surgical procedures.
To align the teeth by correcting malpositions and closing or opening extraction spaces, as well as coordinating the two arches towards good dental engagement, both intra- and post-operatively.

For this, the fixed appliance will include attachments up to the 2nd molar (the molars being banded), with lingual devices placed pre-operatively and intended to achieve bi-maxillary blocking.
The use of continuous arches allows for good transverse coordination and leveling of the arches. On the other hand, segmented arches will be chosen in the case of segmental osteotomies, or to avoid relapse post-operatively, at the level of the incisors which could intrude or egress.

3) Phase 3 “surgical”

Its basic principle lies in the realization of simulations or set-ups on: TLRX, casts and photographs as well as the surgery itself.

4) Phase 4 “post-surgical orthodontics”

If it is plate and screw surgery, it begins 3 to 4 weeks later.
Otherwise, 6 to 8 weeks if it is an intermaxillary fixation.

The objective of this phase is:

To assess the mouth opening and the condition of the appliance after surgery.
To control the restoration of the ICM in RC after removal of the retention gutter which, by default, could be remedied by the use of light and short-term TIM on a flexible arch (.016″ steel, twisted rectangular or NiTi).
The duration of this stage should not exceed 6 to 8 weeks.
To control the transverse direction using a rigid palatal bar or vestibular arch placed in the molar tubes intended for the FEO.
To find the same occlusal objectives of a conventional orthodontic treatment, including the parallelism of the roots if a divergence appears in the case of segmental surgery.

5) Phase 5 “containment and additional treatments”

This involves perfecting and finishing the results obtained after surgery with their maintenance, the duration and type of retention of which vary depending on the initial malocclusion.

IV/- THERAPEUTIC FORECASTS

Once the diagnosis has been made, the treatment plan is established.
The extent of the desired bone, dental arch and soft tissue movements requires them to be objectified through simulations: cephalometric, photographic and simulations of dental arch movements using plaster casts.
The aim of the simulation is:

To guide our therapy.
To visualize the final occlusal result.

The Set-up becomes mandatory and essential in cases of multi-segmental osteotomies where the orthodontist needs references for his preparation.
On the other hand, the Set-up has the advantage of giving the patient an idea of what his face will look like after surgical correction.

V/- INDICATIONS FOR ORTHOGNATHIC SURGERY

All dysmorphoses requiring surgical-orthodontic treatment require:
- Close collaboration between orthodontist and surgeon.
- Programming a precise tactic.
- A very rigorous execution.
The establishment of therapeutic proposals depends essentially on the age of the patient.
The ideal for the orthodontist is to act when the disharmony of the bone bases has been surgically corrected, but surgery cannot be performed at any age, without risking serious disruption to growth or seeing relapses occur.
Furthermore, as long as the dental germs (except the DDS) are still included, an osteotomy cannot be performed at the level of the horizontal branches.
It seems reasonable and prudent to wait until the end of adolescence to operate on excessive disharmonies (promandibulia), therefore around the age of 17 in girls and 18 in boys.
The only exception concerns the anteroposterior displacement of the anterior part of the maxillae, and the posteroanterior displacement of the mandible.
It seems legitimate to be earlier in the presence of a deformation due to insufficient development such as retro-mandibulia, because we can hope that the osteotomy will not stop growth but will facilitate it.
Interceptive surgery at the level of the ascending ramus and condyles may be desirable in the case of unilateral anomalies such as lateromandibular deformity.
When the subject is seen in childhood (which is most common), the first therapeutic phase will be orthodontic (the most effective); it aims to harmonize the arches.
It avoids the temptation to reestablish a functional occlusion.
On the other hand, it corrects so-called compensatory alveolar anomalies (pro, retro) and then comes the surgical stage.
When the subject is only seen later, in late adolescence or adulthood:
- If the malpositions do not prevent proper engagement of the arch, the first step may be surgical. This corrects the misalignment of the bone bases. The second will be orthodontic.
- If the malpositions do not allow good meshing , it is first necessary to reduce orthodontically and then correct surgically .
When the subject presents a significant craniofacial stenosis as in the case of syndromes (APERT, CROUZON), the first gestures will be surgical then orthodontic treatment is carried out.

VI/- CONCLUSION

Nowadays, not a day goes by without the ODF being enriched with a new material, a new technique or an intervention that facilitates and improves its performance.
However, its action is limited and it is necessary to know how to recognize the areas where it cannot venture alone; because of a lack of knowledge or an anomaly that is too extensive, reducing the chances of success.
In these cases, it is necessary to establish the indication for surgical treatment, which cannot itself be carried out without orthodontic advice or collaboration.
A successful orthodontic-surgical intervention is one that meets functional, physiological and aesthetic criteria, while guaranteeing the stability of the results thanks to a stable occlusion.